Hi,
I've solved the problem. In a nutshell: The green signal output on
the ZLXp-E2 had no ground connection. Apparently the original Digital
cable BC13L-10 makes the ground connection internally by shortening the
pins 6,7 and 8 (RED GROUND, GREEN GROUND and BLUE GROUND).
My solution was to solder a short bridge on the ZLXp-E2 between
pins 6 (RED GROUND) and 7 (GREEN GROUND) of the SVGA connector.
(If you want to do this without making the warranty void, you could
as well solder this brige in a SVGA cable which lets you open the
connector).
It works beautifully now and the display is sharp and clear without
shadows. In fact is is even better as with the old PowerStorm 3D10 card :-)
In the case someone is interested, this is how I found this out: I've
disconnected the green cable and suddently the display was clear and
the shadow disappeared (the colors were wrong, of course). This lead me to
the conclusion that the green signal line has an impendance mismatch. With
the monitor disconnected, I've measured the resistance on the BNC
connectors of RED and BLUE and found it to be 75 Ohm which it should have.
The GREEN line, though, had a high impedance!
Thanks to everybody who replied.
Tom
--------------------------- original posting --------------------------
Hi,
Today I have received a new ZLXp-E2 (aka PMAGD-BA) 8MB, 24bpp, 1280x1024,
72Hz video card which I want to use on my PC164LX under Digital Unix 4.0d.
I have an original DEC VRC21-HA monitor which is even listed in the video
card manual as "supported".
Now my problem is that the video quality is so bad that I've put my
old PowerStorm 3D10 (S3 TRIO based, 2MB) card back in. On the blue
SRM console screen, many letters have a red shadow right to them.
Under X the image is blurred as well.
I have an SVGA->5*BNC cable which I've extended by 5 high-quality
75 Ohm (RG-59) cables using 75 Ohm BNC connectors to a total video
cable length of about 6 meters. This extension cable only slightly
reduces video quality with the old PowerStorm 3D10.
But note: The extension cable is *not* the main source of the problems.
I have already tried to connect the monitor without the extended cable
and the video quality only gets slightly better but still is unacceptable.
I have already tried the following without success:
1.) Toggle the termination switch at the back of the VRC21-HA from 75Ohm
to 1KOhm. It gets *slightly* better, but still unacceptable.
2.) Lowered the resolution to 1024x768 and even 640x480. The shadows
right to the letters (only at the beginning of a word, though)
are still there even at 640x480. This leads me to the assumption that
the main problem are the steep signal slopes generated by the ZLXp-E2's
BT463 RAMDAC.
3.) Use the magnetic damper which comes with the card, right at the SVGA
connectors end. No change.
So I'm currently stuck and put the old 3D10 back in, which is really
a pitty.
I think that there *could* be the following ways to solve it:
a.) Get a better and long video cable and get rid of the extension.
b.) Get a suitable adapter which damps the steep video signal slopes.
Some serial resistors should do, IMHO.
So: Is there anyone who can give me some clue what to try next?
Thanks // Tom
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T o m L e i t n e r Dept. of Communications
Graz University of Technology,
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Received on Tue Aug 04 1998 - 10:21:44 NZST